Making gaseous olefines



June 12, 1934. J J GREBE ET AL 1,962,502

MAKING GASEOUS OLEFINES Filed Feb. 6; 1935 juper/veaferw INVENTORS John 7161-866 emldfltblemaw BY :J'ohn 1. Reill ATTORNEY Patented June 12, 1934 PATENT OFFICE MAKING GASEOUS OLEFINES John J.

Grebe, Gerald H. Coleman, and John H.

illy, Midland, Mich. assignors to The Dow Chemical Company, ration of Michigan Midland, Mich a corpo- Application February 6, 1933, Serial No. 655,370.

Claims. (Cl. 260-170) The present invention relates toprocesses for making gaseous oleflnes from mineral oil; and particularly to a process whereby the pyrolysis of such oil is accomplished by intermixing therewith 5 superheated steam as the heat-carrier medium.

By the term mineral oil as used in the specification and claims is meant crude petroleum or liquid fractions and residues thereof, such as kerosene, gasolene, etc.

The cracking of petroleum in the presence of steam to obtain condensable aromatic hydrocarbons and liquid fractions such as gasolene is well known. The present invention distinguishes from 4 such art in that it is concerned with converting mineral oil substantially completely into a gaseous product containing a high percentage of oleflnes.

Numerous methods have been proposed for making gaseous olefines from oils. For instance, it

is well known to pyrolyze oil to obtain oleflnes by exposing the vapors thereof to contact with a highly heated surface, as by passing the oil vapor through an externally heated tube. It has also been proposed to carry out the pyrolysis in the presence of a diluent gas. For example, United States Patent No. 1,726,048 describes a method of producing a gas containing 40 to 50 per cent of oleflnes, nearly exclusively ethylene, by

passing tar-oil vapor in admixture with about an equal quantity of steam through an externally heated iron tube.

In contrast with such procedure we have now found that a much higher yield of gaseous oleflnes can be produced from oil by supplying the heat required for the pyrolysis by mixing with the vapors thereof steam superheated to a temperature and in volume suflicient to produce in the mixture a temperature between about 700 and about 1000 C. in the presence of magnetic iron oxide, and immediately cooling the gaseous products to'a temperature below the point at which polymerization of the oleflnes therein occurs.

To the accomplishment of the foregoing and related ends, the invention, then, consists of the 46 steps hereinafter fully described and particularly pointed out in the claims, the annexed drawing and the following description setting forth' in detail one mode of carrying out the inven- '-tion, such disclosed mode illustrating, however, 50 but one of various ways in which the principle of the invention may be used.

In said annexed drawing: The single figure is a diagrammatic sectional elevation of apparatus adapted to carry out our process.

Our mode of operation comprises vaporizing oil and preheating the vapors thereof to a temperature between 550 and 700 C., preferably about 600-650 C., which may be accomplished with the formation of substantially no decomposition products. The preheated oil vapors are then intermixed with steam superheated to a temperature between about 950 and 1200 0., preferably between 1050 and 1100 C., in amount suflicient to produce in the mixture a temperature '66 between 700 and 1000 0., preferably between 800 and 900 C., in a pyrolyzing chamber containing magnetic iron oxide. In effecting our improved process we obtain practically instantaneous and uniform heating of the oil vapors to the temperature at which gaseous oleflnes are produced therefrom, and avoid any overheating of the vapors with consequent excessive pyrolysis thereof.

The pressure in the chamber may be slightly 15 above atmosphere, e. g. between 0.0 and 5.0 pounds gauge, but the exact pressure is not of particular importance. The mixing of the oil vapor and steam may be accomplished in any convenient manner, for instance, it can be effected so by causing the stream of oil vapor and the steam to impinge at an angle within the pyrolyzing chamber. Thus a thorough and uniform mixing of the oil vapor and steam is obtained as well as practically instantaneous formation of gaseous a5 olefines. The gaseous products are then forced immediately from the pyrolyzing chamber by more oil vapor and steam being supplied thereto. The gases are rapidly cooled to below about 700 C. In this manner overheating or prolonged heating .0 of the oil vapor is avoided, and decomposition thereof to tar or free carbon is substantially eliminated.

The process may be practiced in any suitable form of apparatus, but it will be readily apparent as that a chamber of comparatively large internal cross-section is better adapted to our purpose than a small tube such as is commonly employed for carrying out pyrolytic operations wherein the heat is supplied externally.' The material which may be used for constructing the pyrolyzing chamber is preferably steel of the type such as mild, chrome-vanadium, etc., which is capable of forming magnetic iron oxide upon contact with superheated steam. However, the oxidation-re- 106 sistant high-chromium high-nickel steels are a suitable material, provided that a mass of magnetic iron oxide is maintained in the chamber.

Referring to the drawing, oil is fed through valve-controlled pipe 1 to the pipe-coil 2 wherein ll0 von the oil is vaporized and preheated and then admitted to the pyrolyzing chamber 3. Steam is admitted through the. valve-controlled pipe 4 to the pipe-coil 5 to be preheated and then passed through the superheater passes into the pyrolyzing chamber 3. The oil vapor entering the chamber 3 is instantly pyrolyzed by mixing with the steam from the coil 6, and the gaseous products are immediately forced into the chamber 8 surrounding the pipecoils 2 and 5, thereby cooling the vapors due to indirect contact with the relatively cold incoming oil and steam. A bafiie 9' is provided in the chamber 8 to divide the ascending current oi. gases. The superheater coil, pyrolyzing chamber, and heat interchanger are surrounded by suitable insulation to prevent the material loss of heat therefrom. The cooled vapors then pass from the heat interchanger chamber 8. through the oiT-take pipes 10 into a header pipe 11, and thence into a condensing system to recover the unpyrolyzed oil.

The proportions in which the oil and steam are introduced into the pyrolyzing chamber may be varied over a relatively wide range, depending upon the temperature of each of the materials and upon the temperature to be maintained in the chamber. However, using superheated steam at a temperature of about 1100 C. and oil vapor at about 600 C., the ratio will be about three pounds of steam perv pound of oil to maintain a pyrolyzing temperature of about 875 C. It is readily apparent that the quantity of steam used may be varied from this figure in accordance with well recognized principles, in order to obtain the general range of reaction temperatures herelnbefore set forth.

A coating of magnetic iron oxide can readily be formed on the surfaces of mild steel, etc., in the pyrolyzing chamber by passing superheated steam therethrough for a short time before admitting oil vapor thereinto. In working our process an oxidizing atmosphere is always maintained in the pyrolyzing chamber, due to the presence of considerably more than an equivalent weight of steam relative to the oil, so that reduction of the magnetic iron oxide does not occur. If the pyrolyzing chamber is constructed of material capable of forming magnetic iron oxide it is not necessary that the chamber contain other bodies of the oxide, although it may be found advantageous to loosely pack the space therein with iron turnings, which are readily oxidized, since this aifords more contact surface. We

. have found that the presence of magnetic iron oxide in the chamber positively prevents the formation of free carbon therein during operation of the process. If magnetic iron oxide is not present, hard carbon will gradually accumulate therein and ultimately completely. all the interior of the chamber.

While our preferred mode of operation calls'for vaporizing oil and then preheating the vapors thereof to a temperaturebetween 550 and 700 C. bnfore intermixing with the superheated steam, such procedure is not essential. If desired, the oil may beva'porized or atomized directly by means of the superheated steam simultaneously with being heated thereby to its pyrolyzing temperature. It will be understood that it superheated steam is used to vaporize the oil, as well as effecting the pyrolysis thereof, more through the apparatus may vary with the character of the oil and the pyrolyzing conditions, the range in general being between about 60'and' per cent. Using kerosene, we have obtained 80 per cent of gasiflcation regularly in practice with ordinary control. covered from the pyrolysis product is entirely suitable for re-use in the process, and may be mixed with freshoil fed to the pyrolyzing chamber.

Depending upon the grade of oil used as feed, a yield of gas varying from about to 120 cubic feet per gallon ofoil may be obtained. The total oleiine content in the gas is in excess of 70 per cent by weight and as high as 75 or 80 per cent may be attained under good conditions. A content of 75 per cent. or more of total oleflnes in the gas can easily be maintained in practice. The gas produced contains a high percentage of ethylene, i. e. 40 to 45 per cent by weight.

The condensed oil re- A representative analysis of gas produced ac cording to our improved process is as follows, the figures showing per cent by weight:-

As an example the following detail figures are given which are the average of a number of runs. A kerosene fraction, sp. gr. 0.807, was pyrolyzed at a temperature of about850 C. by admiidng the vapors thereof with superheated steam in the manner described. The steam consumption was 3.5 pounds per pound of oil. 80 per cent of the oil was gasifledat a single pass, the yield of gas being cubic feet per gallon of .oil fed. The gas analyzed 77.3 per cent total oleflnes by weight, of which 42.0 per cent was ethylene and 35.3 per cent propylene and-higher oleflnes.

In a similar series of runs, using a fuel oil, the gas obtained consisted of 71.0' per cent total olefines of which 40.5 per cent was ethylene and 30.5 per cent propylene and higher oleflnes.

Among the advantages which inure to our novel process for making gaseous olefines from mineral oil are--(1) an extremely high percentage of oil is converted at a single pass to a gas very richin olefines; (2) a high over-all conversion' of oil to gas is obtained because the oil is not decomposed to tar or carbon; (3) the thermal efliciency of the process is high because the heat is supplied to the oil directly without having to pass through the walls of the pyrolyzing chamber; and (4) the presence of magnetic iron oxide in the pyrolyzing chamber presents the formation and deposition of carbon therein with consequent plugging thereof.

This application is a continuation-impart of our copending application, Serial No. 518,050, flled 2 February 1931.

Other modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards the process herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

We therefore particularly point out and distinctly claim as our invention:-

1. In a process for making gaseous oleilnes which comprises intermixing oil vapors with sufflcient steam superheated to a temperature between about 950 C. and about 1200 C. to produce in the mixture a temperature of between about 800 and about 1000 C., in the presence of magnetic iron oxide.

2. In a process for making gaseous oleflnes which comprises intermixing oil vapors with sufflcient steam superheated to a temperature between about 950" C. and about 1200 C. to produce 'in the mixture a temperature of between about 800 C. and about 900 C., in the presence of magnetic iron oxide.

3. In a process for making gaseous oleflnes which comprises vaporizing oil, preheating the vapors thereof to a-temperature between about 550 C. and about 700 C., but below the temperature at which substantial cracking thereof begins, and intimately mixing the same with sufilcient superheated steam at a temperature between about 950 C. and about 1200 C. to produce a in the mixture a temperature between about 800 C. and about 900 C., in the presence of magnetic iron oxide.

4. In the process for making gaseous oleflnes from oil, the steps which consist in vaporizing the oil, preheating the vapors thereof to a temperature between 500 C. and 700 C. but below the temperature at which substantial cracking thereof begins, intermixing therewith steam superheated to a temperature between about 1000 C. and about 1100 C. in the ratio of between about 3 and about 4 pounds of steam per pound of oil vapor while in contact with surfaces of magnetic iron oxide, cooling the gaseous product to condense unpyrolyzed oil therefrom and recycling the oil to the first step.

5. In the process for making gaseous olefines from oil, the steps which consist in vaporizing oil, preheating the vapors thereof to a temperature between about 550 C. and 600 C., intermixing therewith steam superheated to a temperature between about 1050 C. and 1100 C. about in the ratio of between about 8 and about 4 pounds of steam per pound of oil vapor while in contact with surfaces of magnetic iron oxide, cooling the gases produced to condense unpyrolyzed oil therefrom, and returning such oil to the first step.

JOHN J. GREBE. GERALD H. COLEMAN. JOHN H. REILLY. 

